Chapter 13 Biochemistry: A Molecular View of Life

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Chapter 13 Biochemistry A Molecular View of Life
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Biochemistry

• Chemistry of living things and life processes
• Cell structural unit for all living things
• Cell membrane defines cell and lets material flow
  into and out of cell
• Plant cells also have walls made of cellulose
• Animal cells do not have cell walls

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Plant Cells
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Animal Cells
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Major Internal Structures

• Cell nucleus contains material that controls
  heredity
• Ribosomes carry out protein synthesis
• Mitochondria produce energy
• Chloroplasts only in plant cells
• Convert solar energy into chemical energy

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Metabolism

• Series of coordinated reactions that keeps cells
  alive
• Catabolism reactions that break down molecules
  for energy
• Anabolism synthesize molecules of living systems

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Carbohydrates

• Sugars, starches, and cellulose
• General formula Cx(H2O)y
• Sugars sweet tasting carbohydates
• Aldoses aldehyde functional group
• Ketoses ketone functional group
• Monosaccharides simplest sugars

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Polysaccharides

• Contain two or more monosaccharides
• Main energy storage system starch
• Plants use them for cell walls cellulose
• Both are polymers of glucose
• Difference in way they are linked together
• Determines chemistry

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Starch

• Two kinds in plants
• Both made of glucose
• Amylose straight chain
• Amylopectin branched chain

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• Glycogen
• Another kind of starch found in animals
• Made of glucose - branched chain
• The structure of glycogen is similar to that of
  amylopectin, although the branches in glycogen
  tend to be shorter and more frequent
• Allows more ends to undergo a more rapid
  hydrolysis to release glucose for energy
  requirement

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• CELLULOSE
• A polymer of glucose molecules with beta linkage
• Beta linkage
• Does not allow for chain of molecules to coil
• Chains can align with one another to form
  fibers
• Fibers can lay down in a criss-cross pattern
• Hydrogen bonding
• Criss-cross pattern gives strength in many
  directions
• Cannot be digested by animals and therefore
  serves
• as dietary fiber to help regulate bowel
  movement

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Lipids

• Defined by solubility
• Insoluble in water
• Fats are largest subgroup of lipids
• Made up of fatty acids and glycerol

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Some Naturally Occurring Fatty Acids
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Saturated vs. Unsaturated Fats

• Saturated fats have no CC bonds
• Saturated with hydrogen
• Unsaturated fats have CC bonds
• May have more than one double bond
• Can add more hydrogen to fats
• React readily with iodine, bromine, and chlorine

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Iodine Number

• Iodine Number number of grams of iodine consumed
  by 100 g of fat

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Proteins

• Serve as structural material for animals
• Required in all living cells
• Composed of carbon, hydrogen, oxygen, and usually
  sulfur

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Amino Acids

• Building blocks for polymers called proteins
• Contain an amino group, NH2, and a carboxylic
  acid, COOH
• Can form zwitterions have both positively
  charged and negatively charged groups on same
  molecule
• 20 required for humans

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Peptide Bond

• Connect amino acids from carboxylic acid to amino
  group
• Produce amide linkage -CONH-
• Holds all proteins together
• Indicate proteins by 3-letter abbreviation

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Sequence of Amino Acids

• Amino acids need to be in correct order for
  protein to function correctly
• Similar to forming sentences out of words

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Structure of Proteins

• Four organizational levels
• Primary structure amino acid sequence
• Secondary structure arrangement of chains around
  an axis
• Pleated sheet
• Alpha helix right-handed helix

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Pleated Sheets
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Alpha Helix
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Tertiary Structure

• Spatial relationships of amino acids relatively
  far apart in protein chain
• Globular proteins compact spherical shape

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Quaternary Structure

• Structure when two or more amino acid sequences
  are brought together
• Hemoglobin has four units arranged in a specific
  pattern

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Intermolecular Forces in Proteins

• Hydrogen bonding
• Ionic bonds
• Disulfide linkages
• Dispersion forces

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Enzymes

• Biological catalysts produced by cells
• Nearly all are proteins
• Enormous catalytic power
• Reactions occur at lower temperatures and at
  higher rates
• Ordinarily highly specific

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Induced-Fit Model of Enzymes

• Explains how enzyme works
• Substrate reacting substance
• Active site where chemical reaction takes place
  and where substrate fits

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Cofactors

• Something other than polypeptide chain required
  by enzyme
• May be metal
• Iron in hemoglobin
• May be organic cofactor
• Coenzyme
• Apoenzyme does not have cofactor

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Inhibition of Enzymes

• Lets cell control when an enzyme works
• Inhibitor binds to allosteric site
• Prevents substrate from binding

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Nucleic Acids

• Serve as information and control center of the
  cell
• Deoxyribonucleic acid (DNA)
• Carries blueprint for proteins
• Found in cell nucleus
• Ribonucleic acid (RNA)
• Carries out protein assembly
• Found in all parts of the cell

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Nucleotides

• Three components
• Sugar
• Either ribose or deoxyribose
• Phosphate unit
• Nucleic acid
• Purines two fused rings
• Pyrimidines one ring

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Nucleotides

• Four bases in DNA
• Pair up in a specific pattern

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DNA

• When all base pairs are paired up with second
  strand form double helix
• Held together by hydrogen bonding

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RNA

• Tends to form single strand
• May pair up with itself

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Genetic Information

• Chromosomes hereditary material, concentrated in
  long threadlike bodies
• 46 in humans
• Made of protein and DNA
• Gene basic unit of heredity
• Section of DNA
• Genome is complete set of genes for an organism

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Self-Replication

• Occurs every time a cell divides

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Transcription

• Converts DNA code to RNA
• Must occur before protein synthesis
• Can make multiple copies to make multiple copies
  of the protein

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Translation

• Converts code on RNA into protein
• Read using base triplet
• Code for amino acids
• Some redundancy

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Polymerase Chain Reaction (PCR)

• Method to rapidly amplify any DNA present in
  sample
• Can use very small amounts of DNA
• Allows for genetic testing
• Cut DNA into relatively small sizes
• Amplify it to see any pattern

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Recombinant DNA

• Allows for addition of genes to organisms
• Make microorganisms produce useful drugs
• All insulin is made this way
• Rapidly change genetics of plants
• Treat genetic disorders in humans

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End of Chapter 15